JP2000273798A - Base paper for release paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base paper for giving release paper that can be directly coated with a pealing solution, for example, an organic solvent silicone, an emulsion silicone or non-solvent silicone or the like in no need of polyethylene laminate and can give release paper having excellent releasing performance and can be regenerated as a papermaking stock. SOLUTION: The base paper mainly comprising wood pulp is coated on at least one face with a pigment coating layer at a weight ratio of the pigment to the binder of 35/65-65/35 at a unit coating weight of 5 g/m2-20 g/m2. Ethylene- vinyl acetate copolymer is used as a binder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base paper for releasable paper, which is recyclable as a base paper for papermaking. In particular, the present invention relates to a solvent-based silicone, a water-based emulsion-based silicone or a solvent-free silicone without using polyethylene laminated paper. The present invention also relates to a base paper for release paper that can be directly coated and can be recycled after use. The base paper for release paper obtained according to the present invention is useful in the fields of general adhesive, tape, casting process paper, molding process paper and the like.

[0002]

2. Description of the Related Art Conventionally, release paper has been produced by applying a release agent such as a silicone resin diluted with an organic solvent such as toluene to a polyethylene laminated paper, glassine paper, clay coated paper, clear coated paper or the like. ing. Further, in recent years, demands for water-based emulsion-type silicones and solvent-free silicones have been increasing as release agents due to environmental problems.

[0003] The characteristics required for release paper base paper include:
Since the silicone resin is very expensive, a small amount of the silicone coating liquid can be uniformly applied. In order to satisfy this requirement, it is important to minimize the penetration of the silicone coating liquid into the base paper. Therefore, the use of polyethylene laminated paper as a base material has been an effective means.

However, since the polyethylene laminated paper has a tough continuous film formed on the surface of the paper, it is difficult to collect the recovered paper as waste paper after use of the release paper and use it as a raw material for papermaking. is there. Further, since polyethylene has a low surface energy, there is a drawback that when an aqueous emulsion silicone is applied, a repelling phenomenon occurs and a uniform coating film cannot be obtained. On the other hand, in the case of release paper using glassine paper, clay-coated paper, or the like as a base material, the barrier property of the base material is insufficient compared to polyethylene laminated paper, so that aqueous emulsion silicone is applied. However, there is a disadvantage that sufficient peeling performance cannot be obtained.

In addition, Japanese Patent Publication No. 1-35959 and Japanese Patent Laid-Open No.
No. 3876 discloses a clay coat type substrate coated with a coating mainly composed of an inorganic pigment and an organic binder as a substrate on which a silicone solution can be directly coated without laminating polyethylene. Have been. Such a base material has an effect of blocking voids on the surface of the base paper, so it can be used to some extent when applying solventless silicone, but it can obtain a high barrier property as required by the present invention. Cannot be used at all and cannot be used for both solvent-based silicone and solvent-free silicone.

JP-A-4-2900, JP-A-4-327300,
And JP 10-1895 A disclose a method of clear coating an aqueous binder such as starch, polyvinyl alcohol (PVA), and a styrene / butadiene copolymer emulsion. However, with these methods,
Although the barrier properties are sufficient, crater-shaped recesses are formed along the gaps in the surface layer of the paper substrate, and the adhesive penetrates into the recesses, so that the peeling performance is reduced. Therefore, there is a disadvantage that the cost increases.

JP-A-6-264038 discloses that the use of a styrene-butadiene copolymer and starch as a binder for a clay coat provides a barrier property to an organic solvent. However, in this case, since a styrene-butadiene copolymer is used as a binder, there is a drawback in that incineration cannot be performed when the styrene-butadiene copolymer deviates from the recycling route.

Further, Japanese Patent Application Laid-Open No. 7-97797 discloses a method of obtaining a release paper having reduced adhesive strength when processed into an adhesive paper by using an acrylic resin as a binder of a clay coat. It is disclosed that it is possible. However, acrylic resins are generally several times more expensive than polyethylene, and are extremely disadvantageous economically. Further, it does not mention that the use of an ethylene-vinyl acetate copolymer as a binder for clay-coated paper provides organic solvent resistance and barrier properties.

[0009]

As described above, base paper for release paper which has not only the coating suitability for solvent-based silicones as polyethylene-laminated paper but also can be recycled as used paper has not yet been put to practical use. In addition, a base paper for release paper which has coating suitability for aqueous emulsion silicone and solvent-free silicone and also has coating suitability for solvent silicone has not yet been put to practical use.

Incidentally, in order to effectively exhibit the release performance, a uniform barrier layer is formed on the surface of the release paper substrate to prevent the penetration of the silicone resin coating solution, that is, the surface of the release paper substrate. It is necessary to suppress the decrease in the peeling force due to the excessive application of the silicone liquid into the void and the penetration of the adhesive into the void by obtaining a smooth surface by noting the void of about 1 to 500 μm.

[0011] Further, in order to reuse the release paper as a papermaking raw material after use, it must be defibrated by a general recycled paper manufacturing process. Furthermore, in consideration of the final disposal that deviates from the recovery route, it is desirable not to contain incineration contraindicated substances such as styrene and acrylonitrile.

[0012]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies to solve these problems, and as a result, have found that voids between fibers on the base paper surface are formed on the base paper surface mainly composed of wood-based pulp fibers. By using an ethylene vinyl acetate copolymer (hereinafter abbreviated as EVA) as a binder which can be sufficiently sealed, and providing a barrier layer composed of a pigment coating layer in which the ratio of pigment to binder is in a specific range. The present inventors have found that a base paper for release paper that can be recycled as used paper can be obtained, and the present invention has been completed.

Accordingly, an object of the present invention is to provide a release paper having excellent release performance by directly applying a release agent such as an organic solvent-based silicone, a solvent-free silicone, or an aqueous emulsion-based silicone. Another object of the present invention is to provide a base paper for release paper that can be recycled as a raw material for papermaking.

[0014]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
5 g of a pigment coating layer mainly composed of a pigment and a binder on at least one surface of a base paper mainly composed of wood pulp fibers.
/ M ² or more and 20 g / m ² or less, wherein an ethylene-vinyl acetate copolymer is used as the binder component, and the mixing ratio of the pigment and the binder is 35/65 by weight. This is achieved by a base paper for release paper, which is characterized in that it is 65/35 or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The base paper mainly composed of wood pulp fibers used in the present invention includes softwood kraft pulp, hardwood kraft pulp, chemical pulp such as sulfite pulp, stone pulp, thermomechanical pulp, mechanical pulp such as refiner grind pulp, In addition, recycled pulp obtained from newspaper, coated paper, high-quality paper, or the like can be appropriately blended. If necessary, non-wood pulp such as kenaf, hemp, bamboo and the like, and fiber material other than cellulose fiber such as glass fiber and polyethylene fiber can be blended.

When making the base paper, internal additives such as a sizing agent, a paper strength enhancer, a fixing agent, a retention aid, a dye, etc., and internal additives such as talc, kaolin, titanium dioxide, aluminum hydroxide, calcium carbonate, etc. Surface treatment is appropriately performed, for example, by adding a filler or applying a paper strength improver such as starch or polyvinyl alcohol, a surface sizing agent, and a dye using a size press, a gate roll, or the like during the papermaking process. It is also possible.

In the present invention, by providing a pigment coating layer using EVA having a very high solvent resistance as a binder on a paper substrate, voids on the surface of the paper substrate can be effectively sealed. In addition, by specifying the blending ratio of the pigment and the binder in the pigment coating layer, it is possible to prevent fine voids in the pigment coating layer, and a base paper for release paper capable of being disaggregated and regenerated by a pulper. can do.

The mixing ratio of the pigment and the binder (pigment binder) in the pigment coating layer in the present invention must be in the range of 35/65 to 65/35 by weight. The mixing ratio is
When the ratio is less than 35/65, the ratio of the adhesive EVA resin is too high, so that the pulper after use as a release paper is inferior and cannot be reused as a raw material for papermaking. Further, since the surface of the base paper for release paper has adhesiveness, blocking tends to occur when the paper is wound up or stored in plain paper. On the other hand, if the compounding ratio is more than 65/35, the resin cannot be sufficiently filled in the pigment and the voids between the pigments, so that many fine voids are generated and the penetration of the silicone resin solution into the coating layer and the substrate is suppressed. I can't do that.

As a binder used in the present invention, an ethylene / vinyl acetate copolymer is used as a main component. If necessary, a binder component such as starch, polyvinyl alcohol, and an acrylic resin is blended in an amount of about 20% of the total amount of the binder. It is also possible. If necessary, a dispersant, a water-proofing agent, a lubricant, an antifoaming agent, a preservative, a dye, and the like can be optionally added to the pigment coating liquid.

The pigment used in the present invention is not particularly limited, but inorganic pigments such as kaolin, talc, mica, titanium dioxide, calcium carbonate, aluminum hydroxide and the like, and organic synthetic pigments such as urea resin may be arbitrarily mixed. It is possible to Further, the coating amount of the pigment coating layer needs to be 5 g / m ² or more, and preferably 20 g / m ² or less.

If the coating amount is less than 5 g / m ² , the voids between the pulp fibers on the surface of the substrate cannot be completely clogged. Can not be suppressed. Also, 20
With a coating amount exceeding g / m ² , good barrier properties can be obtained, but further improvement in quality with an increase in the coating amount cannot be expected, so that it is uneconomical.

As a method for applying the pigment coating liquid to the substrate, a blade coater is preferred because of its high productivity, but various coating apparatuses such as an air knife coater, a rod blade coater, a bar blade coater, and a gravure coater are appropriately selected. be able to.

[0023]

EXAMPLES The present invention will be described below in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In addition, "%" in the examples is all "% by weight",
“Parts” all represent “parts by weight”. In addition, the solvent barrier properties, peeling properties (organic solvent-based silicone, solvent-free silicone, emulsion-based silicone solution) and disintegration properties were evaluated by the following methods.

<Solvent Barrier Property> A 0.1% oil red toluene solution was prepared as a dyeing solution. This dyeing solution was evenly applied to the pigment-coated surface of the sample with a cotton ball or the like, wiped off with a gauze two seconds later, and the state of penetration of the dyeing solution into the coating layer and the paper substrate was observed.

<Removability> 1) Heat addition polymerization type silicone (manufactured by Shin-Etsu Chemical Co., Ltd .: KS
-837) 100 parts of catalyst (Shin-Etsu Chemical Co., Ltd .: CAT-
PL-50T) is prepared by adding 5 parts of a 5% silicone resin toluene solution and applying it to a base paper sample for release paper using a Meyer bar so that the coating amount is 1.0 g / m ² to produce release paper. did. Separately, a high-quality paper having a basis weight of 80 g / m ² was coated with an adhesive (BPS-5127, manufactured by Toyo Ink Co., Ltd.) so as to have a thickness of 125 μm to prepare a surface substrate. The two were bonded and the peeling force was measured under the conditions of a peeling angle of 180 ° and a peeling speed of 1.0 m / min.

2) 100 parts of heat addition polymerization type silicone (manufactured by Shin-Etsu Chemical Co., Ltd .: KM-763) with a catalyst (Shin-Etsu Chemical Co., Ltd.)
Co., Ltd .: PM-3) A 15% silicone resin emulsion aqueous solution to which 2 parts was added was prepared, and the amount of coating was applied to a base paper sample for release paper.
Coating was performed with a Meyer bar so as to obtain a release paper of 1.0 g / m ² . This release paper was bonded to the surface substrate described in 1), and the release force was measured in the same manner as in 1).

3) Silicone prepared by adding 2 parts of a catalyst (PL-56, manufactured by Shin-Etsu Chemical Co., Ltd.) to 100 parts of solvent-free silicone of heat addition reaction type (KNS-320, manufactured by Shin-Etsu Chemical Co., Ltd.) A resin solution was prepared and applied to a base paper sample for release paper by a gravure printing machine so as to have a coating amount of 1.0 g / m ² to prepare release paper. This release paper was bonded to the surface substrate described in 1), and the release force was measured in the same manner as in 1).

<Disintegration> Samples were disintegrated using a Tappi standard disintegrator under the conditions of a sample concentration of 1.5%, a volume of 2.0 liters, and a time of 10 minutes, and the degree of disintegration was compared. Next, a description will be given using examples and comparative examples. Table 1 summarizes the results of quality evaluation of each base paper for release paper.

Embodiment 1 EVA (Sumitomo Chemical Co., Ltd .: SF
-455) For 40 parts, kaolin (made by CADAM: Amazon 8)
8) A pigment coating liquid having a solid content of 60% was prepared by appropriately mixing 60 parts and a dispersant, an antifoaming agent, and a lubricant. This coating solution was applied to high quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater to prepare a base paper for release paper having a coating amount of 15 g / m ² .

As a result of evaluating the base paper for release paper by the above-described method, a solvent barrier property comparable to that of the polyethylene laminated paper of Comparative Example 1 described later was obtained. Good release suitability was obtained when any of the solvent-based silicone, emulsion-based silicone and solvent-free silicone was applied.
In addition, the disintegration was good, and the paper could be recycled as a raw material.

Embodiment 2 FIG. EVA (Sumitomo Chemical Co., Ltd .: SF
-455) For 50 parts, kaolin (made by CADAM: Amazon 8
8) A pigment coating liquid having a solid content of 60% was prepared by appropriately mixing 50 parts and a dispersant, an antifoaming agent, and a lubricant. This coating solution was applied to high quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater to prepare a base paper for release paper having a coating amount of 15 g / m ² .

The base paper for release paper was evaluated by the above-mentioned method. As a result, a solvent barrier property comparable to that of the polyethylene laminated paper of Comparative Example 1 described later was obtained. Good release suitability was obtained when any of the solvent-based silicone, emulsion-based silicone and solvent-free silicone was applied.
In addition, the disintegration was good, and the paper could be recycled as a raw material.

Embodiment 3 FIG. EVA (Sumitomo Chemical Co., Ltd .: SF
-455) For 60 parts, kaolin (made by CADAM: Amazon 8
8) A pigment coating liquid having a solid content of 60% was prepared by appropriately mixing 40 parts and a dispersant, an antifoaming agent, and a lubricant. This coating solution was applied to high quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater to prepare a base paper for release paper having a coating amount of 15 g / m ² .

The base paper for release paper was evaluated by the above-mentioned method. As a result, a solvent barrier property comparable to that of the polyethylene laminated paper of Comparative Example 1 below was obtained. Good release suitability was obtained when any of the solvent-based silicone, emulsion-based silicone and solvent-free silicone was applied. In addition, the disintegration was good, and the paper could be recycled as a raw material.

Comparative Example 1 A polyethylene laminated paper in which low-density polyethylene having a thickness of 20 μm was laminated on the high-quality paper used in the examples was prepared as a base paper for release paper. As a result of evaluating the base paper for release paper by the method described above, very good solvent barrier properties were obtained, and good release suitability was obtained when a solvent-based silicone release agent was applied. However, when the emulsion silicone was applied, repelling of the release agent occurred, and sufficient release performance was not obtained. In addition, since the polyethylene laminate layer remains in a film state, it cannot be recycled as a papermaking raw material.

Comparative Example 2 EVA (Sumitomo Chemical Co., Ltd .: SF
-455) For 30 parts, kaolin (made by CADAM: Amazon 8
8) A pigment coating liquid having a solid content of 60% was prepared by appropriately mixing 70 parts with a dispersant, an antifoaming agent, and a lubricant. This coating liquid was applied to a high-quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater to prepare a base paper for release paper having a coating amount of 15 g / m ² . As a result of evaluating the base paper for release paper by the above-mentioned method, the solvent barrier property equivalent to that of the example could not be obtained. Further, even when any of the solvent-based silicone, emulsion-based silicone and solvent-free silicone was applied, good release suitability could not be obtained.

Comparative Example 3 EVA (Sumitomo Chemical Co., Ltd .: SF
-455) For 70 parts, kaolin (made by CADAM: Amazon 8)
8) A pigment coating liquid having a solid content of 60% was prepared by appropriately mixing 30 parts and a dispersant, an antifoaming agent, and a lubricant. This coating liquid was applied to a high-quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater to prepare a base paper for release paper having a coating amount of 15 g / m ² .

The base paper for release paper was evaluated by the above-mentioned method, and as a result, a solvent barrier property comparable to that of the polyethylene laminate paper of Comparative Example 1 was obtained. Good release suitability was obtained when any of the solvent-based silicone, emulsion-based silicone and solvent-free silicone was applied. However, since the binder ratio was high, the disintegration property was poor, and it was impossible to recycle as a papermaking raw material.

Comparative Example 4 EVA (Sumitomo Chemical Co., Ltd .: SF
-455) For 50 parts, kaolin (made by CADAM: Amazon 8
8) A pigment coating liquid having a solid content of 60% was prepared by appropriately mixing 50 parts and a dispersant, an antifoaming agent, and a lubricant. This coating liquid was applied to a high quality paper having a basis weight of 75 g / m ² and a thickness of 100 μm using a test blade coater to prepare a base paper for release paper having a coating amount of 4.0 g / m ² . As a result of evaluating the base paper for release paper by the above-mentioned method, the solvent barrier property equivalent to that of the example could not be obtained. In addition, when any of the solvent-based silicone, emulsion-based silicone, and solvent-free silicone was applied, good release suitability could not be obtained.

[0040]

[Table 1] As is apparent from Table 1, satisfactory results were obtained for the release paper base papers of the respective examples according to the present invention, whereas the release paper base papers of the comparative examples were not satisfactory in some properties. It was a good result.

[0041]

The base paper for release paper of the present invention has a solvent barrier property comparable to that of polyethylene laminated paper, and good release performance can be obtained even when a solvent-based silicone resin is applied. In addition, since it has a good affinity for solvent-free silicone and emulsion silicone as compared with polyethylene laminated paper, good releasability was obtained even when these release agents were applied. In addition, it has a disintegration property that cannot be obtained with polyethylene laminated paper, and can be reused as a papermaking raw material. Therefore, the present invention has great industrial significance.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Takashi Yamaguchi 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Manufacturing Co., Ltd. (72) Inventor Toshifumi Narushima 1-30-1 Kamiochiai, Shinjuku-ku, Tokyo No. 6 Japan Paper Manufacturing Co., Ltd. Product Development Laboratory F-term (reference) 4J004 DA04 DB02 4L055 AG27 AG59 AG64 AG89 AH02 AH37 AJ04 EA14 EA32 FA30 GA43

Claims (1)

[Claims] 1. A base paper for release paper comprising a base paper mainly composed of wood pulp fibers and a pigment coating layer containing a pigment and a binder as main components provided on at least one side thereof in an amount of 5 g / m ^{2 to} 20 g / m ^2. A base paper for release paper, wherein an ethylene-vinyl acetate copolymer is used as the binder component, and the mixing ratio of the pigment and the binder is 35/65 or more and 65/35 or less by weight. .